Computing networks can include multiple network devices such as routers, switches, hubs, servers, desktop PCs, laptops, and workstations, among other peripheral devices, e.g., printers, facsimile devices, and scanners, networked together across a local area network (LAN) and/or wide area network (WAN).
In addition to physical connections, networks often form virtual, e.g., logical connections. A virtual LAN (VLAN) is a logical subgroup within a LAN that is created via software rather than manually moving cables in the wiring closet. It combines user stations and network devices into a single unit regardless of the physical LAN segment to which they are attached and allows traffic to flow more efficiently within populations of mutual interest.
VLANs are implemented in port switching hubs and LAN switches and generally offer proprietary solutions. VLANs reduce the time it takes to implement connection moves, additions and changes. VLANs function at layer 2 of the open system interconnection (OSI) protocol stack. The OSI protocol stack is one example of the set of protocols used in a communications network. A protocol stack is a prescribed hierarchy of software layers, starting from the application layer at the top (the source of the data being sent) to the physical layer at the bottom (transmitting the bits on the wire). The stack resides in each client and server, and the layered approach lets different protocols be swapped in and out to accommodate different network architectures. Layer 2 is the data link layer. Layer 2 is responsible for node to node validity and integrity of the transmission. The transmitted bits are divided into frames; for example, an Ethernet, Token Ring or FDDI frame in local area networks (LANs).
Link aggregation control protocol (LACP) is a standard in IEEE 802.3ad which defines a method of aggregating links together to form a more redundant link with larger bandwidth. An aggregate link, also known as a “trunk”, is formed either manually or dynamically. A manual trunk comes into existence when a network administrator physically configures LACP on multiple network devices that are connected together with a set of links, e.g., physical (Layer 1) connections. A dynamic trunk can come into existence when an administrator has previously configured multiple network devices to support “dynamic” LACP, and when two or more links are connected between the switches.
One issue with LACP is that manual trunks are configured on a per port basis, so when a link is moved from one port to another a reconfiguration has to take place. This involves administration action, which may be costly and prone to human error. One issue with dynamic trunks is that the trunk becomes a member of the default VLAN when it is formed and may have no awareness of VLANs on a given device. With previous LACP approaches the dynamic trunks are restricted to the default VLAN which means that ports which were previously either “tagged” or “untagged” members of multiple VLANs may lose this previous membership. This fact becomes a drawback in modern multiple VLAN environments.